This invention relates to the field of contoured cartons molded to essentially finished shape by the suction deposition of fibrous pulp materials from an aqueous slurry thereof against screen-covered, open-face forming molds, followed by subsequent drying, and known as molded pulp cartons. A tremendous number of different styles of molded pulp cartons have been proposed for packaging a wide range of commodities, but this invention is particularly concerned with cartons designed for the retail merchandizing of fragile articles such as eggs, light bulbs, electron tubes, Christmas tree ornaments, and the like. Companion but mutually inconsistent requirements for such cartons are good cushioning qualities for the fragile articles, and good printability qualities for retail merchandizing purposes.
Cartons molded of fibrous pulp material are particularly suitable for packaging fragile articles, because molded pulp has non-compacted consistency, resilient softness, and an irregular fibrous feel and appearance which imparts desirable cushioning characteristics to the carton. Many different styles of such molded pulp cartons for fragile articles such as eggs have been proposed, many of which have narrow ribs arranged in generally vertically radial array within one or more of the egg pockets, for various purposes. Representative thereof are the egg cartons disclosed in patents such as: Chaplin U.S. Pat. No. 2,423,756 issued July 1947; Chaplin U.S. Pat. No. 2,560,847 issued July 1951; Schilling U.S. Pat. No. 2,600,130 issued June 1952; Grant U.S. Pat. No. 2,885,136 issued May 1959; Reifers U.S. Pat. No. 3,016,176 issued January 1962; Reifers U.S. Pat. No. 3,145,896 issued August 1964; Reifers U.S. Pat. No. 3,185,370 issued May 1965; Reifers U.S. Pat. No. 3,207,409 issued September 1965; and, Snow U.S. Pat. No. 3,398,875 issued August 1968. None of these types of disclosures, however, suggest the concept of an egg carton having the cover printability advantages attained by the carton of the present invention.
One problem common to egg cartons, such as those disclosed in the aforesaid patents wherein the closeable cover is integrally hinged to the pocketed bottom, is that the cover, and particularly the outer surface thereof, has the non-compacted consistency, resilient softness, and irregular fibrous feel and appearance present in the inner surface of the egg pockets. The reason for this, of course, is that the closeable cover, being integrally hinged to the pocketed bottom, is formed on the same molding apparatus by the same method as the pocketed bottom. The inevitable result is that the outer surface of the cover is not well adapted to receive printing for the important purpose of including advertising and other information on the visible outer surface of the closed cover, because it is well known that the rough, cushiony surface of molded pulp does not lend itself to the reception of printed matter, particularly high resolution printing including small letters and other details.
This problem has been recognized for a long time, and one approach to avoiding it is to pre-print separate labels on paper capable of receiving high resolution printing, and then glue the labels to the covers of the molded pulp cartons -- an expensive and cumbersome procedure at best.
Another approach to solving it is disclosed in Randall U.S. Pat. No. 2,704,493 issued March 1955 wherein the egg carton is molded on conventional apparatus according to the conventional method wherein the carton is first formed against an open-face suction mold, and then dried in a free space such as being placed on a conveyor and moved through a heated drying oven, but then the finished, dried carton is subjected to an "after-pressing" operation wherein the dried cartons are pressed in the presence of heat and moisture between a pair of mating molds only to the extent sufficient to remove warpage and distortion and provide an improved surface finish while retaining the cushioning characteristics obtained by the free drying. While this improves the printing capabilities over cartons which are simply free dried without after-pressing, the smoothly ironed surface of the cover nevertheless inherently retains some of the cushioning characteristics obtained by the initial free drying which tends to defeat optimum printing requirements, and the after-pressing inherently removes some of the rough fibrous cushioning attributes from the inner surface of the egg pockets which tends to defeat optimum egg protecting requirements. The aforesaid Randall patent thus discloses a useful compromise between "free-dried" or "open-dried" rough finished articles, on the one hand, and "die-dried" or "closed-dried" molded pulp articles on the other hand, both of which are explained therein.
The terms "free-dried" or "open-dried" as used herein include not only the use of flat conveyors for moving the cartons through the drying oven, but also the use of open-face warpage-preventing forms on the conveyor for holding the cartons as they are moved through the drying oven. Such warpage-preventing forms are known from disclosures such as the aforesaid Reifers U.S. Pat. No. 3,185,370, and are to be contrasted with "die-drying" or "closed-drying" processes.
The "die-dried" or "close-dried" molded pulp articles are quite different, and are made for instance by apparatus and according to a method such as that described in Randall U.S. Pat. No. 2,183,869 issued December 1939. These articles are dense, hard, boardy, and inferior in cushioning and resilient qualities, but extremely smooth-finished for the reception of even very high resolution printing. Such die-dried molded pulp articles have been made and sold in the form of disposable plates, bowls and the like under the trademark "CHINET" for many years by Keyes Fibre Company of Maine, U.S.A.
Egg cartons heretofore have not been made by "die-dried" or "closed-dried" processes, however, not only because it is a more expensive procedure, but because the inner surface of the egg pockets would be hard and board-like and would not have the non-compacted consistency, resilient softness and irregular fibrous feel and appearance required for acceptable egg holding and protecting purposes.
Thus, the problem heretofore unresolved by the prior art is the ability to produce a one-piece molded pulp egg carton wherein the inside of the egg pockets have the resilient softness desirable for proper egg holding and protecting capabilities, and the outside of the cover has a smooth feel and appearance desirable for aesthetic characteristics including the ability to receive high resolution printing.